The present invention relates to a magnetic head to be used in connection with a recording medium having a large coercive force such as a metal tape, and more particularly to a so-called metal-in-gap (MIG) type magnetic head whose magnetic core comprises a ferrite core having a high magnetic permeability and a metallic magnetic film having a high saturation magnetic flux density.
Recently, in the magnetic recording art for use in computer systems, a so-called MIG type magnetic head equipped with a ferromagnetic metallic film having a high saturation magnetic flux density is proposed and put into practical use in connection with heightening the recording density and frequency of the information signal. A conventional MIG type magnetic head will be described hereinbelow with reference to FIG. 12.
In FIG. 12, the conventional MIG type magnetic head basically comprises high magnetic permeability ferrite cores 1 taking an opposed relation to each other and metallic magnetic films 2 including nitrogen, having a high saturation magnetic flux density and disposed at the insides of the ferrite cores 1 to take an opposed relation to each other. Between the metallic magnetic films 2 there are provided SiO2 films 4 which are in turn joined through a PbO based low-melting-point glass film (junction film) 5 to each other. This junction film 5 and the SiO2 films 4 make up a magnetic gap. Numeral 6 designates a bonding glass.
In the case of a thin film medium having Hc&lt;1500 (Oe), the metallic magnetic film 2 made of an Fe-Al-Si based alloy (Sendust alloy), Co based amolphous alloy or others which has a high saturation magnetic flux density of about 10 KG is put into practical use. On the other hand, in the case of a thin film medium having Hc.gtoreq.1500 (Oe), the recording and reproduction of an information signal cannot sufficiently be affected with such a metallic magnetic film of about 10 KG. Thus, the metallic magnetic film is required to have a higher saturation magnetic flux density.
One possible solution is to use a metallic magnetic film made of an Fe-metal-N based material as described in the Japanese Patent provisional Publication No. 54-94428. In a MIG type magnetic head using a metallic magnetic film made of the Fe-metal-N based material (metal denotes at least one-of metallic elements belonging to the IVa group, Va group, VIa group in the periodic table), for improving the soft magnetic characteristic of the Fe-metal-N based alloy, the junction between the ferrite core halves is made at a temperature of about 500.degree. to 600.degree. C. This thermal junction is also for the thermal treatment. However, in the aforementioned conventional arrangement, when constructing the MIG type magnetic head with the Fe-metal-N based alloy by melting and adhesion, there is a problem that the nitrogen of the Fe-metal-N based alloy film is bubbled in the bonding glass 6 (close to the metallic magnetic film 2) by the heating as shown in FIG. 13. Concurrently with making its appearance worse, the bubbles 100 lower the strength of the glass itself whereby many cracks occur in manufacturing to deteriorate the yield of the products. According to an analysis, the nitrogen also-exists between the metallic magnetic film 2 and the SiO2 film 4. It is considered from this that the nitrogen from the metallic magnetic film 2 due to the thermal treatment flows into the bonding glass 6 along the SiO2 film 4 to generate the bubbles 100 therein. Or it is considered as the nitrogen flows from an area 102 (FIG. 13) of the metallic magnetic film 2 into the bonding glass 6.
The Japanese Patent provisional Publication No. 1-185810 discloses a technique to remove bubbles existing in a glass through metallic films additionally provided on metallic magnetic films. However, the metallic magnetic films do not include nitrogen and the metallic films are not arranged to prevent the nitrogen of the metallic magnetic films from flowing into the glass to generate bubbles therein when performing the thermal treatment.